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A2 Biology Revision…read more

Slide 2

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On the wild side
Unit 5…read more

Slide 3

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The very incomplete equation for
Enters the plant
through Has 3 main purposes-
the stomata To keep the plant turgid
To act as a solvent for reactions
Is a source of electrons in non-Cyclic
How is it simplified?
·Photosynthesis occurs in two stages, the light independent reaction and light
dependant reaction.
·Glucose is not the only useful product.
·Co2 and H2O never meet.…read more

Slide 4

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· Photosynthesis takes place in the CHLOROPLASTS of plant cells.
The thylakoid
membrane contains
Light independent photosynthetic pigments
system (calvin like chlorophyll which
cycle) happens absorb light energy.
Fluid filled
Light dependant system
takes place here…read more

Slide 5

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How photosynthesis really works.
· In the thylakoid membrane of chloroplasts we have photosystems
that contain pigments such as chlorophyll.
· Accessory pigments absorb energy and pass it on to
the chlorophyll making it "excited". pigments
· This causes it to release electrons up to a higher energy Primary
level. chlorophyll
· Which stimulates photolysis- the splitting of water into protons and
electrons to replace those lost from the chlorophyll.
· The electron from this is then given to photosystem 2 where it
replaces one that has got excited.
· The excited electron from PS2 then passes down the electron
transport chain- a series of carrier proteins. This is known as a redox
reaction and releases energy which can be used to synthesize ADP
into ATP.
· Meanwhile in PS1, another electron is excited and goes up an
energy level.
· This either creates energy in the electron transfer chain before
returning to photosystem 1 (cyclic photophospholrylation).
· Or combines with hydrogen ions released during the photolysis of
water to turn NADP into NADPH.
· This is the LDR and happens in the thylakoid. It produces oxygen as
a waste product and ATP and NADPH which are taken to the Calvin
cycle which is the next stage of photosynthesis.…read more

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Calvin Cycle
· Happens in the stroma.
· CO2 combines with a 5 carbon carrier known as RUBP
catalysed by rubisco.
· This creates a very unstable 6 carbon molecule which quickly
breaks down into two 3 carbon molecules known as GPs or
Glycerate 3-phospate.
· GP is then Turned into TP (triose phosphate). This is done
using energy in the form of ATP from the LDS. The reduction
also requires hydrogen ions which are taken from the NADPH
produced in the LDS.
· Five out of every 6 turns of the calvin cycle are used to produce
RUBP to restart the cycle again. However every 6 turns make
one glucose molecule and other organic substances such as
carbohydrates, Lipids, Amino acids and nucleic acid.…read more

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Amazing! Thanks 

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